Combustors of gas turbine engines are subject to high temperatures and effusion holes can be used to direct air to cool combustor components such as combustor liners, domes and heat shields. Effusion holes extend through the component at a shallow angle with respect to the surface of the component, for efficiently cooling without risking a reduction in combustion temperatures. A typical effusion hole is designed to be a straight cylindrical passage. The length of the hole is dictated by the thickness of the component such as the combustor liner and the angle of the effusion hole with respect to the combustor liner surface. In conventional effusion cooling, heat is removed from, for example the combustor liner, via three mechanisms: backside convection cooling, in-hole convection cooling, and film cooling. Due to the limited thickness of the combustor liner and thus the limited length of the cooling passages formed by the effusion hole, effusion cooling performance is traditionally more dependent on a film cooling mechanism than on the in-hole convection cooling. Nevertheless, it is sometimes desirable to make the overall hole cooling system less dependent on a film cooling mechanism, particularly in regions where the cooling film tends to mix with the hot gas, rather than flowing along the combustor liner surface.
Accordingly, a cooling system having improved cooling holes for enhanced cooling performance is desirable.